Patello-femoral joint replacement is a well known orthopedic surgical procedure. A variety of conventional joint replacement devices have been in use since the 1970's, however, unlike joint prostheses, which are typically used in total knee replacement surgery, conventional patello-femoral joint replacement devices have not been widely accepted in the orthopedic community. This may be due to the somewhat mixed clinical results that conventional patello-femoral joint prostheses have demonstrated as presented in the pertinent medical literature. The conventional prostheses typically include femoral components that were larger, bulkier devices contoured to fit the trochlear groove of the femur. Their contoured geometry, however, made it almost impossible to develop a precise method of preparing the diseased surface of the femur to fit the geometry of the implant. Typically the surgeon when using conventional patello-femoral joint replacement devices has to use powered burrs to carve out the boney surface to accept the implant. This makes the fit and alignment of the implants hard to reproduce, and somewhat variable from case to case. This method, and the large size of the implants, also led to difficulties, if and when, it may be necessary to revise the implant. It is not uncommon for it to be necessary to revise the implants to total knee replacements in later years as the arthritis progresses. For this reason the ability to easily perform a revision procedure without excess sacrifice of bone is crucial.
The use of precise cutting guides for other knee replacement procedures slowly came into practice in orthopedics in the early 1980's. Similar improvements in the devices and methods used in patello-femoral joint replacement have not been seen. Prior to the present invention, there have not been methods or surgical devices that permit accurate, reproducible bone cuts in the replacement of the patello-femoral joint.
Early attempts to improve the devices used in patello-femoral joint replacement include those described in U.S. Pat. Nos. 4,007,495 and 4,151,615. Both of these early patents describe patello-femoral joint replacements, but they do not address the method, or instrumentation required to implant the products. Similarly, U.S. Pat. No. 3,878,566, which describes a commercially successful patello-femoral joint device, provides no improvement in the method of implanting the device as it simply discloses that the prosthesis is implanted by simply burring out a spot for it in the bone. There is no disclosure of a means or method for aligning or guiding the surgeon's preparation of the bone for improved implantation of the device. U.S. Pat. No. 5,609,644 includes claims, which are drawn to a patello-femoral joint, however, only the patellar replacement component is described in any detail and no device or method is disclosed that would assist the surgeon in the accurate implantation of the device.
U.S. Pat. Nos. 5,571,196 and 5,824,098, both issued to Stein, attempt to address this need by describing a system of instrumentation that includes an intramedullary guide rod and a router frame for preparing a trough in the anterior femur. The system disclosed by Stein does not retain the anatomical contour of the femur and requires several additional steps in the operation thereby making the process more complicated and more prone to complications. The method of Stein is also far more invasive that the present invention, and, unlike the present invention, once implanted would not allow an uncomplicated revision, if necessary, since the machined femoral trough taught by Stein is much more bone sacrificing and is not aligned with standard total knee geometries.
These prior art attempts to provide a patello-femoral joint replacement system have all failed to incorporate a low profile femoral implant design with geometrically defined angular surfaces similar to those in the femoral components of total knee replacements, combined with a series of simple precise cutting guides, that provide accurate, reproducible cuts.
In response to this need the present invention described herein has been developed.